Test-tube embryos may save rhinos

06 Juillet, 2018, 21:16 | Auteur: Therese Cote
  • A northern white female rhinoceros named Najin at Ol Pejeta Conservancy in Kenya in 2015

For the first time, scientists have managed to create hybrid embryos of the northern white rhino (NWR) - the world's most endangered mammal.

A 28-year-old rhinoceros named Najin and her daughter, Fatu, are the only northern white rhinos on the planet.

Except maybe they won't be the last. If they run out of supply or the northern rhinos meet an untimely end, there may be no going back.

An worldwide team of scientists has successfully created hybrid in vitro embryos, combining the almost extinct northern white rhinos and its relative species, the southern white rhinos.

However, with sperm available from just four male Northern White Rhinos, the scientists say this method alone won't be enough to restart a genetically diverse, self-sustaining population.

"Over the past few years, the sperm from three bulls was sampled and put in cryopreservation".

But now, scientists have developed new assisted reproductive technologies (ARTs) which could provide the beleaguered species with a lifeline.

"Our results are solid, reproducible and very promising". The ultrasound-guided device is placed trans-rectally.

The study titled, "Embryos and embryonic stem cells from the white rhinoceros", was published July 4 in the journal Nature Communications.

If the embryos are to be implanted in a surrogate, the researchers stated that southern white rhinos would carry the new rhino hybrids to term.

The device developed by Professor Hildebrandt, who is also an Honorary Professor at the University of Melbourne and lead author of the paper, is now awaiting patent approval and could also be used to collect eggs from other large mammals.

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Over the decades, the population of northern white rhino kept declining due to extreme poaching.

It is also resident in several zoos around the world.

Although such hybrid embryos are not pure northern white rhinoceros, the researchers were able to show for the first time that the creation of such embryos is possible.

The next step in the process was bringing the eggs to maturity, which was done under laboratory conditions, in much the same way as the eggs of many other species, including humans. This is a three-person job requiring a steady hand that can guide a needle of just over 1 millimetre in diameter and nearly 1 metre in length into the reproductive system via the rectum to capture the eggs.

The northern white rhinoceros needs a miracle.

"The northern white rhino sperm, when they were thawed out, were not very good and had to be activated by an electrical stimulus", says Professor Renfree. For now, these early embryos, called blastocysts, have been frozen.

In the meantime, the team will practice, implanting some of their hybrid embryos into SWR surrogates "to test the system".

The embryos have been frozen for now, but Hildebrandt and his colleagues hope to eventually impregnate a female southern white rhino as a surrogate. "In a second step these germ cells will then be transformed into eggs and sperm", explain Dr Sebastian Diecke, stem cell expert at the Max Delbrueck Center for Molecular Medicine in the Helmholtz Association (MDC) in Berlin, Germany, and Prof Katsuhiko Hayashi, stem cell expert at the Department of Stem Cell Biology and Medicine, Kyushu University, Japan.

This is why they have the ambitious plan to extract the eggs from living NWR females first and then breed the hybrid white rhinos.

"They are infertile and never produced offspring, but they do have oocytes and these could be grown up in culture".

"This is a proof of concept project". Theresult was production of viable embryos comprising of genetic material from a functionally extinct sub-species.

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